The present invention relates to an optical module which is formed by integrating an optical element, optical waveguide, or the like, and a method of manufacturing the same.
An optical module is a transducer from electrical energy to light, or from light to electrical energy. An optical module is constituted in hybrid integrated form by an optical element, an optical waveguide, an electronic circuit, and the like. Optical modules are used, for example, in an optic fiber communications system. A conventional optical module is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-237016.
This optical module uses a surface emission laser as the light-emitting element. The surface emission laser is formed on a semiconductor substrate. The light is emitted in the direction perpendicular to the plane of this semiconductor substrate. As a result, when this optical module has the surface emission laser mounted on the mounting substrate, light is emitted in the vertically upward direction. Therefore, the optical fiber must be attached to the mounting substrate so as to face vertically upwards. Therefore, the thickness of the optical module is increased to the extent that the optical fiber extends upwards.
Electronic instruments are required to be thinner. Naturally, therefore, optical modules are also required to be thinner.
The present invention solves this problem. The object of the present invention is the provision of an optical module and method of manufacturing the same, such that the optical module can be made thinner.
The present invention provides an optical module comprising: a mounting member; and an optical element mounted on a plane of the mounting member, the optical element is formed on a semiconductor substrate, emits light in a direction perpendicular to the plane of the semiconductor substrate, and admits light from a direction perpendicular to the plane of the semiconductor substrate; and the optical module further comprises an optical waveguide mounted on the plane of the mounting member and guiding light emitted from the optical element or light admitted to the optical element; the optical element is mounted so that light emitted from the optical element or light admitted to the optical element travels in a direction along the plane of the mounting member; and the optical waveguide is mounted along the plane of the mounting member.
The optical module of the present invention has the optical element mounted so that the light travels in a direction along the plane of the mounting member. Therefore, the optical waveguide can be disposed so as to be along the plane of the mounting member. According to the present invention, the optical module can be made thinner than the conventional optical module in which the optical waveguide is oriented vertically.
In the optical module of the present invention, the optical element may have an optical aperture from which light is emitted or to which light is admitted, and the optical aperture may be oriented along the plane of the mounting member. When the optical element is oriented in this way, the light travels in a direction along the plane of the mounting member.
The optical module of the present invention may have a positioning member for positioning the optical element mounted on the plane of the mounting member. Without the positioning member, the size of the optical element must be designed so that the optical element and optical waveguide are positioned properly when the optical element is connected with the optical waveguide. By providing a positioning member, the optical element does not need to be mounted on the plane of the mounting member. Therefore, the design freedom of the size of the optical element is increased.
It should be noted that the material of the positioning member may be a material of high thermal conductivity. Because the heat of the optical element can be released, that is to say, be subject to heat sink treatment. The material of the positioning member may be an electrically conductive material. Because it can be used as an electrode. In this case, as a particular material for the positioning member may preferably be used, for example, copper or the like.
The optical module of the present invention may include a semiconductor chip mounted on the plane of the mounting member and electrically connected to the optical element, and the positioning member may be mounted on a side surface of the semiconductor chip.
In the optical module of the present invention, the positioning member may be positioned lower than the semiconductor element formation plane of the semiconductor chip.
As a method of mounting the positioning member on the side surface of the semiconductor chip, the use of an adhesive may be considered. In this case, the adhesive may spread out from between the positioning member and the side surface of the semiconductor chip. In this event, when the positioning member is positioned on a level same as or higher than the semiconductor element formation plane of the semiconductor chip, the adhesive may adhere to the semiconductor element formation plane of the semiconductor chip. On the semiconductor element formation plane, an electronic circuit is formed from semiconductor elements. Therefore, for example, when the adhesive is electrically conductive, the electronic circuit may be shorted.
It should be noted that when there is an excess of adhesive between the positioning member and the side surface of the semiconductor chip, there is a risk of the positioning member being inclined. Should this occur, the positioning member will not be able to be precisely adhered to the side surface of the semiconductor chip. Therefore, a space for absorbing excess adhesive may be provided between the positioning member and the side surface of the semiconductor chip. As means of forming the space, of the surfaces of the positioning member, a foot portion may be provided or a recess may be formed on a surface contacting the side surface of the semiconductor chip.
The material properties of the adhesive may be selected, depending on the characteristics required of the adhesive, from electrical conductivity, electrical insulation, thermal conductivity and thermal insulation.
In the optical module of the present invention, the mounting member may include a first interconnect, and the positioning member may contact the first interconnect. As described above, the positioning member may function as an electrode or function as a heat sink. By the positioning member contacting the first interconnect, the positioning member can be made to function as an electrode. When the positioning member is functioning as a heat sink, heat can flow from the positioning member to the first interconnect. Therefore, the heat releasing effect is further improved.
The mounting member may include a second interconnect, and an electrode of the optical element may extend to the second interconnect, and be electrically connected to the second interconnect.
Wire bonding may be considered as means for electrically connecting the upper electrode and the second interconnect. When the upper electrode is not facing vertically upwards, high level wire bonding technology is required. As a result of disposing the optical element so that the light travels in a direction along the plane of the mounting member, it may no longer be possible for the upper electrode to face upwards. In this case, by applying the structure that the upper electrode extends to the second interconnect, the electrical connecting portion between the upper electrode and the second interconnect is made easy.
In the optical Module of the present invention, the optical module may be packaged by sealing with a light-blocking resin, and an optical path between the optical element and the optical waveguide may be filled with a light-transmitting resin. By packaging the optical module with resin, the general applicability and ease of handling of the optical module are improved. The reason for a light-blocking resin is used is that there is a risk of malfunction of the electronic circuit when natural light or light from an optical element reaches the electronic circuit mounted on the mounting member. However, the optical path is assured by filling the location forming the optical path with light-transmitting resin.
The optical module of the present invention may further comprise a mounting surface to be mounted on another mounting member, and the optical waveguide may extend in the direction along the mounting surface.
The present invention further provide a method of manufacturing an optical module, the optical module comprising; a mounting member; and an optical element mounted on a plane of the mounting member, and the optical element is formed on a semiconductor substrate, emits light in a direction perpendicular to the plane of the semiconductor substrate, and admits light from a direction perpendicular to the plane of the semiconductor substrate; the optical module further comprises an optical waveguide mounted on the plane of the mounting member and guiding light emitted from the optical element or light admitted to the optical element; the method comprises: a step of disposing the optical element so that a side surface of the semiconductor substrate faces a plane of the mounting member; a step of electrically connecting an upper electrode of the optical element to another electrode; and a step of disposing the optical waveguide in a direction along the plane of the mounting member.
The upper electrode of the optical element is positioned on the plane of the semiconductor substrate of the optical element. Therefore, when the optical element is disposed so that the side surface of the semiconductor substrate of the optical element faces the plane of the mounting member, the upper electrode faces horizontally. When the upper electrode of the optical element is electrically connected to another electrode, for example, by wire bonding, mounting the optical waveguide previously impairs the connection. However such a problem does not occur in the present invention, because the optical waveguide is disposed on the plane of the mounting member after electrically connecting the upper electrode to another electrode.